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    <title>Document</title>
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        <script>
            var num1 = prompt('请输入值')

            switch(true){
                case num1<=100 && num1>= 90:console.log('你的成绩是A');
                break
                case num1<=89 && num1>= 80:console.log('你的成绩是B');
                break
                case num1<=79 && num1>=70:console.log('你的成绩是C');
                break
                case num1<=69 && num1>= 60:console.log('你的成绩是D');
                break
                case num1<=59 && num1>=0:console.log('你的成绩是E');
                break
            }
        </script>
</body>
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